Ocarinas have the great advantage over recorders that you can safely play them without hearing protection. I have personally measured the loud notes on both a soprano recorder and an alto recorder and the SPL meter measured over 100dB(A) at the ear (indoors, so this includes reverberation too, but most recorders are played indoors). Note that standard recorder fingering allows for almost no control over dynamics; each note has a single set volume that it must be played at to sound in tune. (Advanced technique allows slight control over dynamics with alternative fingerings.) For this reason I do not think recorders should be used in schools.